The present invention relates to an electrical surgical knife which may be inserted into a body cavity of a patient, for instance, to cut an affected part. More particularly, the invention relates to an improved electrical surgical knife device a specific feature of which resides in its electrical insulating means.
As is well known in the art, an electrical surgical knife is operated as follows. High frequency electric power is applied across the plate side of the knife which is brought into contact with the skin of a patient and the positive polarlity side of the knife the edge of which is brought into contact with the affected part. As the high frequency current flows collectively through the edge of the positive polarity side, Joule heating is generated at the edge. This heat is utilized to burn or cut the affected part.
A device including both an electrical surgical knife and an endoscope for treating an affected part of the body cavity which the operator cannot see directly has been put in practical use. In a conventional such device, the positive polarity side circuit of the surgical knife, which is relatively long, upon being inserted into the body cavity extends along the wall of the body cavity. Therefore, the circuit must be electrically well insulated. For this purpose, the positive polarity side circuit line is covered with a silicon tube. However, high frequency current sometimes leaks through pin holes in the covering tube which may damage a part of the wall of the body cavity.
In order to prevent the occurrence of such problems due to current leakage, means for forming a short-circuit of leakage current have been proposed in which the metal blade of the flexible pipe of an endoscope into which the positive polarity side is inserted and the endoscope body, which is integral with the metal blade, are electrically connected to the aforementioned plate side which is brought into contact with the skin of a patient.
However, it should be noted that, with the conventional construction, high frequency leakage currents flow in the endoscope body and, if the patient or the operator touches the endoscope body carelessly, he may be shocked or burnt by current which flows through his body to ground.
Accordingly, an object of the invention is to provide an electrical surgical knife device in which the above-described problems due to the leakage current problems accompanying a conventional device of this type are prevented.